The present invention relates to electron tube bases and particularly to those for electron tubes having a relatively small diameter neck. The improved base is particularily useful in color picture tubes of the plural beam shadow mask type, but the invention cam be used in any electron tube wherein a small stem with a large exhaust tubulation is desired, e.g., in large power tubes.
In most of the rectangular, 110.degree. deflection, color picture tubes presently in use, the triple beam electron gun is mounted in a tubular glass neck having an O.D. of about 11/8 inches and terminating at an annular transverse wall, through which 12 stiff leads extend in a circle and from which a central exhaust tubulation extends.
The small diameter of the tube neck presented problems with respect to the protection of the leads from accidental bending during shipment and storage. In addition, with the smaller tube neck, the leads were in closer proximity to one another and protection from surface leakage had to be provided. The conventional tube bases, such as shown in U.S. Pat. No. 3,219,965 issued Nov. 23, 1965 to Joseph B. D'Adamo, which were essentially caps through which the leads extended, did not provide a solution. In response to these unsolved problems, the tube base was modified as evidenced by Canadian Patent No. 928,761 issued on June 19, 1973 to Richard H. Hughes. The modified base was a hollow cylinder with external longitudinal grooves having semicircular channels, extending the full length of the groove. The tube leads would fit within the channels after the base was assembled on the socket. The portion of the cylinder between the grooves protected the pins from damage and electrically insulated them from one another. The matching socket had 12 spring contacts corresponding to the 12 leads. When the socket was slipped on the base, the contacts initially slid on the bottom of the groove which formed the rim of the channel. When the spring impinged the lead, it would rise onto the lead.
However, problems developed with the use of these modified bases. Removal of the socket from the base often pulled the base from the tube neck. Investigation disclosed that during removal, the spring contact in the socket would slip from the bottom of the groove into the channel and wedge against the channel walls. This wedging in essence would lock the base on to the socket causing both to be pulled off the tube neck.